The mitigation for Speculative Store Bypass (SSB) - CVE-2018-3639 is not enabled by default after installing the respective patches mentioned in ADV180012. The necessary keys required to enable mitigation on both Clients and Server are:

QID 91462 primarily focuses to help customers identify if the mitigation for CVE-2018-3639 is not enabled by checking for the above registry key values. The above registry key settings will also have Spectre Variant 2 (CVE-2017-5715 "Branch Target Injection") and Meltdown (CVE-2017-5754) mitigations enabled.

The registry key values can be set accordingly by customers to enable/disable patches for the Spectre and Meltdown mitigations. The flexibility was provided by Microsoft to help customers test the updates in their environment for any performance and other issues before they are deployed.

Note: Selectively customers who do not want mitigations for Spectre Variant 2 (CVE-2017-5715 "Branch Target Injection") and Meltdown (CVE-2017-5754) on Windows Client can do so by setting above registry values accordingly to disable protections.

Reference Screenshot mentioning mitgation for CVE-2017-5715 and CVE-2017-5754 must be enabled to receive full protection Servers:

Microsoft has disabled the protections by default on Windows Server to help customers first evaluate the updates in their environment to check for any performance issues based on which they can enable updates or keep them disabled.

Note: Customers can also enable protections for Spectre Variant 2 (CVE-2017-5715 "Branch Target Injection") and Meltdown (CVE-2017-5754) only by setting the values for the above mentioned registry keys accordingly.